In some applications it is desirable to measure changes in an electromagnetic field (“EMF”) environment surrounding an inductive coil. These measured changes can be used in a sensor to detect the presence of magnetic materials. A conventional sensor for measuring changes in an EMF environment is an inductor-capacitor (“LC”) oscillator circuit. The LC circuit can be charged by running current through it, and then letting the LC circuit oscillate freely. The resulting oscillation of energy creates an oscillating waveform, which can be observed by an application. The relative dampening of this waveform reflects changes in the perceived inductance of the coil in the LC circuit. When a metallic object is close to the coil, the LC oscillator dissipates its energy faster because of the inductive coupling the coil forms with the metallic object. The magnetic coupling results in more rapid decay of the waveform envelope. The decay or fall off of the waveform envelope can be quantified to produce an inductive sensor signal.
A conventional approach for measuring changes in an EMF environment uses an Analog Comparator with a tuneable reference level often generated by a digital-to-analog converter circuit (“DAC”). The analog comparator can be used to compare the waveform to the DAC-generated reference, and a mechanism then counts the number of times the oscillating waveform and reference voltage intersect. This count can be used as the inductive sensor's signal.
Although the conventional analog approach works, using analog components can result in an expensive circuit design that may not be easily adapted to other applications.